#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>

 struct TreeNode {
     int val;
     struct TreeNode *left;
     struct TreeNode *right;
 };

struct TreeNode* invertTree(struct TreeNode* root) 
{
    if(root == NULL)
        return NULL;
    struct TreeNode* tmp = root->left;
    root->left = root->right;
    root->right = tmp;
    invertTree(root->left);
    invertTree(root->right);
    return root;
}